WO2018127434A1

WO2018127434A1 - Method and system for ensuring antenna contact and system function in applications of detecting internal dielectric properties in a body

Info

Publication number: WO2018127434A1
Application number: PCT/EP2017/084411
Authority: WO
Inventors: Andreas Fhager; Mikael Persson; Harald Jacobsson; Rikard VINGE
Original assignee: Medfield Diagnostics Ab
Priority date: 2017-01-09
Filing date: 2017-12-22
Publication date: 2018-07-12

Abstract

In a method for determining antenna fit of at least one antenna (105) positioned outside a body (103) microwave signal(s) are transmitted from the at least one antenna (105) towards the body (103). At least the body (103) and a surrounding medium (107) have different dielectric properties. A first part of the microwave signal is first reflected and/ or scattered from the surface of the body (103) and a second other part is entering the body (103). The reflected and/or scattered microwave signal(s) are received at another antenna (105) or at the transmitting antenna (105). The received microwave signal(s) are compared to another microwave signal or a criterion. Based on the comparing, it is determined if the at least one antenna (105) is fit to the body (103) or not.

Description

METHOD AND SYSTEM FOR ENSURING ANTENNA CONTACT AND SYSTEM

FUNCTION IN APPLICATIONS OF DETECTING INTERNAL DIELECTRIC PROPERTIES IN A BODY

TECHNICAL FIELD

Embodiments presented herein relate to ensuring good contact and sufficient quality of measured signals in a system indented for detecting or monitoring of status in internal parts of the body, e.g. the brain and in particular to using electromagnetic radiation in the microwave region.

BACKGROUND Non-invasive techniques for diagnosis and determination of status of humans or animals are increasingly winning ground since these poses low risk for the patient and are usually low cost as compared to invasive techniques. Especially considering the brain, noninvasive techniques may provide convenient and safe ways of determination of the brain status. However, the common techniques for this are not able to determine all types of parameters of need, which means that there are blind spots where invasive techniques are still used.

Furthermore, some non-invasive techniques provide solutions where the patient is still put in risk of danger, for instance where x-rays are used the patient will be subjected to a dose of radiation potentially harmful and it can in many cases not be used for continuously or semi-continuously, i.e. intermittently, monitor the status of parameters in the brain or in any other part of the body.

The use of conventional non-invasive techniques for pre-hospital applications is limited, for example Computed Tomography (CT) and Magnetic Resonance Imaging (MRI) systems are too large and costly for ambulance use. Other already portable systems, such as ultrasound systems, are not always suitable for the particular diagnostic need. New portable systems for pre-hospital use are therefore needed. Detection of haemorrhages in the brain caused by any form of head trauma, or detection of haemorrhages in any other part of the body could be made with the same underlying technology. In the head, intracranial bleedings constitute a risk of developing lethal intracranial pressure. In severe cases, such as traffic accidents, patients might develop lethal intracranial pressure within one or two hours. These patients can often be treated successfully with surgical or other interventions in the treatment is started early after the injury. It requires transportation to the right hospital where such neuro-surgery expertise is available. A person with an intracranial bleeding might initially look healthy seem unaffected and there is a significant risk that these patients get transported to a closer hospital without neuro-surgery expertise. This will likely be lethal for the patients. If the presence of an intracranial bleeding is detected too late the patient might be dead before arriving at a hospital where neuro-surgery interventions could have saved the life of the patient. The underlying challenge here is that no system exists at present that with sufficient accuracy can diagnose or predict which patents have suffered head trauma that have led to an intracranial bleeding.

The standard method to detect intracranial bleedings is by CT or MRI, but this has to be done at hospitals and thus valuable time is lost before treatment can be started. Other experimental techniques for pre-hospital diagnostics exist and are under clinical evaluation, but no systems showing adequate sensitivity and specificity of haemorrhages have yet reached the market.

Delays in diagnosing stroke patients is today a major problem as many patients do not get a diagnosis in time, and therefore treatment are often significantly delayed with dramatic consequences for the patients. Delays in the treatment increase the risk of severe injuries, handicaps, and even death.

Ambulance service paramedics are trained to use a stroke recognition tool to speed up transfer and assessment of patients with suspected stroke. This facilitates the time critical intervention of thrombolysis which has been shown to improve the outcome from ischemic stroke if given in time. Even with the best efforts today, many patients still don't get the treatment in time. It is also difficult to distinguish between healthy people and stroke patients, and further to diagnose between ischemic and hemorrhagic stroke. With portable systems that could diagnose between ischemic and hemorrhagic strokes in a pre-hospital setting many patients could get better treatment and thereby the patient outcome could be better. As an example, the possibility to diagnose patients with ischemic stroke from patients with hemorrhagic stroke would enable to better optimize the initial management of the patients. It would also be possible to consider giving clot resolving medicine patients with ischemic stroke before reaching the hospital.

Other example where today's technology does not provide any solution is for long term monitoring of patients with an increased risk of getting a stroke. Monitoring of high risk patients during sleep or while the patient lies down in bed would be a helpful tool in early detection of a potential stroke. In patients that have had an intracranial bleeding monitoring is a way to detect if the bleeding starts over. There exist also a number of other monitoring situations where it is of interest to monitor the occurrence, presence, or changes in a present bleeding, or other types of liquids, e.g. edemas. Applications, such as bedside monitoring of intracranial pressure would also be desired in many clinical situations. Neither CT, MRI or ultrasound are suitable or practical for these type of monitoring applications. CT is also unsafe as it would expose the patients for long periods of x-ray exposure.

Apart from the above-mentioned limitations in today's technology for detecting internal properties related to medical conditions in patients, there are several applications in industry where today's technology has significant limitations to detect internal properties or changes of different internal bodies.

To exemplify, there has been an increased demand from wood processing industry for non-destructive techniques to detect and quantify internal defects and variations in trees and wood products. Sensor systems are of interest to the wood and timber industry where different choices in the phases of thinning, logging and at the sawmill affect the net production and thus the revenue of the industry. For example, information about the interior of the wood could be used for optimizing the different phases of the production chain and with automatized and easy to use systems the optimization could be made down to individual logs. In the forest, it could be advantageous to determine the quality of the trees before thinning, or logging. Trees could for example be affected by tree rot which cannot be seen from the outside but seriously degrades the quality of the tree. Such trees should ideally be removed already when thinning the forest. The possibility of identifying internal defects, such as knots and nails, can help optimize the production and to avoid costly damage to the saw blade and other tools.

EP2020915B1 describes a method and a system to reconstruct images from microwave measurement rata.

EP2032030B1 describes a device, method, and system for monitoring the status of an internal part of a body using an electromagnetic transceiver operating in the microwave regime; microwave measured signals in from of time domain pulses are analysed to determine the location of the surface of the body (e.g. skin) and thereby enable compensation for movements.

EP2457195 B1 describes a device for determining an internal condition of a subject by analysis of an enclosed volume, by using a particular statistical classification algorithm, using training data.

US 7,226,415 B2 describes an apparatus for detecting blood flow based on the differences in dielectric properties of tissue. US 6,4547,1 1 B1 relates to a haemorrhage detector. It describes an antenna array including matching medium between antennas and the skin, as well as damping material between antennas. The detection algorithm is based on analysing time domain pulses and their changes du to haemorrhages. US 7,122,012 B2 describes a method of detecting a change in the level of fluid in tissue. The analysis is based on comparing the measurements with reference measurements on a target without the liquid present. The presence of fluid is based on differences between a base line signal and a measured signal. US 9,072,449 B2 disclose a system for wearable/man-portable electromagnetic tomographic imaging includes a wearable/man-portable boundary apparatus adapted to receive a biological object within, a position determination system, electromagnetic transmitting/receiving hardware, and a hub computer system. US 9,414,749 B2 discloses an electromagnetic tomography system for gathering measurement data pertaining to a human head includes an image chamber unit, a control system, and a housing. The image chamber unit includes an antenna assembly defining a horizontally-oriented imaging chamber and including an array of antennas arranged around the imaging chamber. The antennas include at least some transmitting antennas and some receiving antennas. The control system causes the transmitting antennas to transmit a low power electromagnetic field that is received by the receiving antennas after passing through a patient's head in the imaging chamber. A data tensor is produced that may be inversed to reconstruct a 3D distribution of dielectric properties within the head and to create an image. The housing at least partially contains the antenna assembly and has a front entry opening into the imaging chamber. The head is inserted horizontally through the front entry opening and into the imaging chamber.

US20150342472A1 discloses a method of assessing status of a biological tissue includes irradiating an electromagnetic signal, via a probe, into a biological tissue. The irradiated electromagnetic signal is received after being scattered/reflected by the biological tissue. Blood flow information pertaining to the biological tissue is provided, and the received signal is analyzed based at least upon the provided blood flow information and upon knowledge of electromagnetic signal differences in normal, suspicious, and abnormal tissue. Using a dielectric properties reconstruction algorithm, dielectric properties of the biological tissue are reconstructed based at least upon results of the analyzing step and upon blood flow information, and using a tissue properties reconstruction algorithm, tissue properties of the biological tissue are reconstructed based at least in part upon results of the reconstructing step and upon blood flow information.

Therefore, there is a need to at least mitigate or solve the above issues SUMMARY

It is an object of the present embodiments to remedy at least some of the problems associated with performing measurements in a microwave based system for detecting internal properties in a body. A particular challenge in a microwave diagnostic system is to ensure good contact between the antennas and the body, to ensure good coupling with matching media used between antennas and body, to ensure good functionality of attenuating materials between antennas, and to detect faulty antennas and cables before measurements are made. The embodiments presented herein offer at least some solutions to that problem.

This is provided for in a number of aspects in which a first is a device for obtaining information of antenna contact with the skin and antenna health and system status before making measurements for determining status of internal parts of a body part.

According to a first aspect, the object is achieved by a method for determining antenna fit of at least one antenna positioned outside a body. The body is surrounded by a medium. At least the body and the medium have different dielectric properties. One or multiple microwave signal(s) are transmitted from the at least one antenna towards the body. A first part of the microwave signal leaves the antenna and is first reflected and/or scattered from the surface of the body and a second other part is entering the body. The one or multiple reflected and/or scattered microwave signal(s) are received at another antenna or at the transmitting antenna whereby it is operated as a receiver after it has transmitted or operated as a receiver at the same time as it is transmitting. The received microwave signal(s) are compared with at least one other microwave signal or a criterion determined from measurements of the received microwave signals when the at least one antenna is known to be fit to the body. Based on the comparing, it is determined if the at least one antenna is fit to the body or not.

According to a second aspect, the object is achieved by a system for determining antenna fit of at least one antenna positioned outside a body. The body is surrounded by a medium. At least the body and the medium have different dielectric properties. The system is adapted to transmit one or multiple microwave signal(s) from the at least one antenna towards the body. A first part of the microwave signal leaves the antenna and is first reflected and/or scattered from the surface of the body and a second other part is entering the body. The system is adapted to receive the one or multiple reflected and/or scattered microwave signal(s) at another antenna or at the transmitting antenna whereby it is operated as a receiver after it has transmitted or operated as a receiver at the same time as it is transmitting. The system is further adapted to compare the received microwave signal(s) with at least one other microwave signal or a criterion determined from measurements of the received microwave signals when the at least one antenna is known to be fit to the body. The system is adapted to, based on the comparing, determine if the at least one antenna is fit to the body or not.

Embodiments herein afford many advantages, of which a non-exhaustive list of examples follows:

While typically not used in the field of diagnostics, microwave signals are useful for various applications which require diagnosis. Microwave signals provide a non-invasive measurement deep into different types of bodies. Such measurements may provide useful information that is otherwise invisible to the human eye. Such non-invasive techniques for diagnosis and determination of status of bodies pose low risk for the object, e.g. a patient, and are involved with a low cost as compared to invasive techniques

On advantage of the embodiments herein is that techniques based on microwave signals provide non-invasive, easy access, to bodies such as e.g. a human brain at a relatively low cost providing a large amount of multi frequency scattering signals that can be used to analyze the continued developments of the dielectric and geometric properties of the body. A further advantage is that a system based on microwave technology relatively easily can be built portable and light-weight. This makes the microwave technique particularly useful for pre-hospital diagnosis in for example ambulances or at an accident scene. Microwave technology is also suitable for the development of hand held units for field use, for example in the forest.

A further advantage of the embodiments herein is that in principle, all conditions inside a body where there is a dielectric contrast with respect to the surrounding dielectric properties and/or where the level of dielectric contrast changes over time may be detected.

Another advantage of the embodiments herein is that they provide solutions for ensuring best possible quality of the measured microwave scattering signals. That provides more reliable measurement result for interpretation. Another advantage of the embodiments herein is that they provide solutions for ensuring good contact between the antenna and the body, a chance for adjustment is given. During monitoring of patients, the same method is used to ensure that good contact between antennas and body is maintained. That increases quality of the measured signals.

Another advantage of the embodiments herein is that they provide solutions for ensuring good contact and coupling of a matching medium that is placed between the antenna and the body. A misplaced or faulty matching medium will be detected and the operator can be notified and make appropriate adjustments. That increases quality of the measured signals

Another advantage of the embodiments herein is that they provide solutions for ensuring functioning of the damping of microwave signals propagating between antennas. A misplaced or faulty damping material lead to lower quality of the measured signals. If such errors are detected and the operator notified it is possible to make appropriate

adjustments of the damping material. In that way quality of the measured signals are improved as direct signals between antennas (signals propagating outside the body of investigation) are undesired and lowers the quality of the measured signals. The embodiments herein are not limited to the features and advantages mentioned above. A person skilled in the art will recognize additional features and advantages upon reading the following detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following the embodiments will be described in a non-limiting way and in more detail with reference to exemplary embodiments illustrated in the enclosed drawings, in which:

Fig. 1 Illustrates schematically the components of the embodiment presented herein.

Fig. 2a-d Illustrate schematically four different minimal configurations of the

embodiments presents herein. Fig. 3 illustrates 8 antennas configured around a body for detection of an internal object and where the embodiments described herein are arranged to ensure good contact between the antenna(s) and the body. Fig. 4a Illustrates 8 antennas configured around a body where matching material is used between the antenna(s) and the body.

Fig. 4b illustrates 8 antennas around a body with a damping material is used

between antennas.

Fig. 5 shows the received microwave signals from three different measurements together with criterion.

DETAILED DESCRIPTION

The embodiments described herein relate to sensing of internal objects inside a larger object. It is accomplished by illuminating the larger object with electromagnetic radiation that is propagating through and scattered from the different immersed objects. The scattered radiation is carrying the information utilized an analyzed for the purpose of detecting and analyzing possible objects, e.g. abnormalities inside. The large object could be a skull, a torso, a leg or some other body part. But the objects could also be non-living tissue, and of non-biological origin, such as but not limited to wood, plastics etc. The embodiments described herein are related to detecting non-optimal configurations of the antennas and components of the system on the body.

Some components of the system described herein are depicted in Figure 1 and consists of at least one transmitting antenna 105t and at least one receiving antenna 105r. When using the reference number 105 without the letters t or r, it refers to any of the transmitting and receiving antennas. It should be noted that these two antennas 105 may be combined in one antenna and in such case a directing mechanism (not shown) may be arranged in the path between the antenna 105 and the microwave transceiver inside the transceiver or as an external device. The combined transmitting and receiving antenna 105 may be referred to as a transceiver. The directing mechanism may be used in order to not transmit directly into a receiving unit in the transceiver possibly saturating the input electronics. A combination of the microwave transmitting/receiving unit 13 and the analyzer 14 may have a direction dependent component, e.g. the directing mechanism, which controls the transmitted and received signal in different directions. This may take place at the same time, i.e. transmission and reception may take place simultaneously. The directing mechanism may also be referred to as a switching mechanism. The transceiver may comprise two more or less separate units, a transmitting unit and a receiving unit, or it may be built into one single unit with electronics for each function built into the single unit. The antennas are connected to a microwave transmitting/receiving unit 13 that is adapted to transmit and receive microwave signals to and from the antennas 105. The system may further comprise an analyzer 14 that is arranged to control a display unit 15. The display unit 15 is adapted to display the analyzed result of the signals e.g. on a screen. Signal analysis may be performed at another location by sending, through a network connection or using storage devices, measured signals to another analysis device, e.g. a central server or central computational device for post analysis and/or for storing of measured signals in a central storage facility. This analysis device may the same as the analyser 14 in figure 1 or a different analyser. The detection result based on the embodiments described herein, indicating the system status and the presence of gaps and spaces 1 15 between the antenna 105 and the body 103 or indicating that no spaces 1 16 are present together with system status, is presented for example on a screen comprised in the display unit 15 where an operator views the information and can make relevant adjustments to the system, before diagnostic measurements are made. The operator can also be notified that the system is in functioning as intended and measurements can be made. The operator may also be referred to as a user.

The received/scattered microwave signals are collected for instance from continuous waves, measured at single or multiple discrete frequencies, or from pulsed or p-n sequences, by the microwave transmitting/receiving unit 13. The measured

received/scattered signals are spanning a given and pre-defined frequency range. The frequency range is for example but not limited to 100 MHz to 10 GHz or more. The frequency interval can be narrower but also wider. Based on the measured signals, transmitted and/or reflected signals, for example but not limited to S-parameter data are calculated in the microwave transmitting/receiving unit 13 or in the analyzer14 based on the transmitted and received microwave signals. Other representations of the microwave signal are in form of z-, y-, h-, t- parameter or ABCDE-parameters, reflection coefficients, insertion loss, a percentage parameter, a magnitude parameter, a phase parameter, a time-domain pulse or any other representation of the received microwave signal.

An system comprises at least one antenna configured to at least transmit microwaves, i.e. electromagnetic waves. The antenna may also be configured to receive microwaves. In one example, the system may comprise at least one transmitting antenna 105t and at least one receiving antenna 105r. The system may constitute the interface to the body 103 under investigation. The at least one antenna 105 in the system is adapted to be placed outside the object under investigation and is arranged to send electromagnetic signals into the body. The antennas transmitting and receiving the microwaves may be connected to a signal generator and a signal receiver respectively in a microwave transmitting/receiving unit 13. The signal receiver may be connected to the transmitter and receiver 13. One or more receiving antennas 105 outside the object under investigation are detecting the scattered radiation which later may be processed by an algorithm for signal analysis and diagnosis. Antennas 105 can be monopoles, patches, horns, etc. or any type of antenna. Other types of emitters and or receivers can be used.

In Figures 2a-d the system is illustrated to comprise at least one antenna 105. The system may be seen as to constitute the interface between the system 105 and the body 103. The body 103 may comprise an internal object 100. The antenna 105 is adapted to be placed outside the body 103 and arranged to send microwave signals into the body 103. The antenna 105 transmitting and receiving the microwave signals may be connected to a signal generator and a signal receiver in the microwave

transmitting/receiving unit 13 respectively. The microwave transmitting/receiving unit may also be adapted to constitute two or more separate units with the signal generator and a signal receiver located in different locations. One or more microwave

transmitting/receiving unit 13 may be adapted to be located outside the body 103 and detects the scattered radiation which may be later processed for signal analysis and diagnosis with the purpose to detect an internal object 100 in the body 103, or alternative to determine if no internal object 100 is present. The body 103 and antenna 105 are surrounded by a background medium 107, which in most cases and measurement situations would be air, but other media are possible. One measurement scenario, illustrated to the left in Figure 2a, may be when the antenna 105 is in contact with the body 103, when a space 1 15 between the antenna 105 and the body 103 is unwanted and when it is desired to identify such space 1 15 in order to avoid measurements with a space 1 15 between the antenna 105 and the body 103. The purpose with the embodiments described herein is to provide means to detect and thereby provide a possibility to adjust the antennas and to ensure that the measurements are made in a situation as illustrated in the right part of Figure 2a, when there is no space 1 16 between the antenna 105 and the body 103.

In one embodiment, described in Figure 2a, the system consists of a configuration of at least one antenna 105 acting both as transmitter and receiver.

In another embodiment, described in Figure 2b, the system may consist of a configuration of one antenna 105 acting both as transmitter and receiver and with a matching medium 1 1 1 , in the following referred to as the first dielectric material 1 1 1 , between the antenna 105 and the body 103. The purpose of the matching medium is to improve the coupling of microwave signals and fitting of the antenna 105 to the body. Another purpose of the matching medium may be to allow adjustments of the antenna 105 and to accommodate different sizes and shapes of the body 103. The first dielectric material need to be fitted to the antenna 105 and the body 103. The spaces 1 15 between the antenna 105 and first dielectric material 1 1 1 , and/or between the body 103 and first dielectric material 1 1 1 , should be avoided. A space may also be referred to as a gap. Such spaces 1 15 may be detected, in addition to other defects, such as cracks, changed in the dielectric properties that might develop over time, etc. in the first dielectric material. One purpose with the embodiments described herein may be to provide means to detect and thereby provide a possibility to adjust the antennas and to ensure that the measurements are made in a situation as illustrated in the right part of Figure 2b, when there is no space 1 16 between the antenna 105 and the first dielectric material 1 1 1 or the first dielectric material 1 1 1 and the body 103.

In another embodiment, described in Figure 2c, the system may consist of a configuration of one antenna 105 acting both as transmitter and receiver and where the antenna 105 is surrounded by a damping material 1 13, in the following referred to as the second dielectric material 1 13. The purpose of the second dielectric material may be to shield the antenna 105 and to attenuate disturbances and to stop microwave signals from propagating on the outside of the body 103 or to propagate into the background medium 107 as such signals will lower the quality of the measured microwave signals. For detecting internal objects 100 it is an advantage if all measured signals have propagated through the body 103 and if no microwave signals propagate outside the body 103 as this gives less disturbances in the received/scattered microwave signals, and higher accuracy in the detection of internal objects 100. Spaces may be detected between the body 103 and the second dielectric material 1 1 1 , and between the antenna 105 and the second dielectric material 1 1 1 . Also, other defects in the second dielectric material can also be 5 detected, such as cracks or changes of the dielectric properties that occur over time.

In another embodiment, Figure 2d, the system may consist of at least one separate transmitter antenna 105 and at least one separate receiver antenna 105 positioned around the body 103. Or in yet another embodiment it consists of at least two antennas 10 105 acting both as transmitters and receivers. A possible operation may be that all

antennas in turn, are used as transmitters while the rest of the antennas are receiving. The figure 2d also illustrates use of a first dielectric material 1 1 1 and a second dielectric material 1 13. Fitting of antennas 105, first dielectric material 1 1 1 and second dielectric material 1 13 in relation to the body 103 can be determined.

15

The illustrations in Figures 2a-d are examples of operator configurations of the system. An operator can choose, depending on the type of body 103 and internal object 100, the most suitable configuration for that particular application and therefore either have the antennas 105 in direct contact with the body 103 or to use a first dielectric material 1 1 1 as a

20 matching medium. The operator can further choose to use or not to use a second

dielectric material 133 between antennas 105 for damping. The system may be used to detect faults, defects and to detect that the fitting of antennas 105, first dielectric material 1 1 1 and second dielectric material 1 13 is in order before microwave measurements are started, or during monitoring measurements made over longer periods of time.

25

Figure 3 illustrates an example system with 8 antennas 105 that can be operated as transmitters and/or receivers. Figure 3 illustrates the system positioned outside a body 103. The antennas 105 are depicted at a distance, which could be as small as 1 mm or smaller, leaving a space 1 15 between the from the body 103 and the antenna 105.

30

Figures 4a and 4b illustrate an example system with 8 antennas 105 that can be operated as transmitters and/or receivers. Figures 4a and 4b illustrate the system positioned outside the body 103. In figure 4a, the antennas 105 are depicted at a distance, leaving a space 1 15 between the body 103 and the antenna 105 and with a 35 second dielectric material 1 13 between the antennas 105 for damping of unwanted microwave signals propagating outside the body 103. In figure 4b, the antennas (105) are depicted with a first dielectric material 1 1 1 between the body 103 and the antenna 105. In figures 4a and 4b, it may be of interest to determine whether the antennas 105 are properly fitted to the body 103, or whether the first dielectric material 1 1 1 and/or that the second dielectric material 1 13 is properly fitted between the antennas 105.

The microwave measurement system, consisting of antennas 105, microwave

transmitting/receiving unit 13, analyzer 14, display 15, and possibly also a first dielectric material 1 1 1 and second dielectric material 1 13, described herein may be setup to generate microwave signals and make microwave measurements that are used to calculate, for example but not limited, to S-parameter data in the desired frequency range between the transmit-receive antenna combinations. Note that S-parameters are only an example parameter. Other examples of common representations of measured signals that could work equally well are z, y or h-parameters, reflection coefficients, insertion loss, etc. Signals can be collected at one or more frequencies in the range. Signals collected in time-domain or in frequency domain are both related by the Fourier Transformation. From a point of signal analysis, the two different sets of signals are of equal value. The measurement electronics for frequency domain measurements or pulsed measurements may differ, but could equally well be used.

The measured signals, represented for example as the calculated S-parameter data, may be transferred to an analyzer 14. The analyzer 14 may extract the necessary information from the measured signals and processes them in order to perform assessment of the fitting of the antennas 105 and/or the first dielectric material 1 1 1 and/or the second dielectric material 1 13, before a result is presented at the display unit 15. The display unit 15 is illustrated in figure 1 .

In Figure 5, some principles for the detection of the fitting of the antennas 105 to the body 103 and/or the first dielectric material 1 1 1 and/or that the second dielectric material 1 13 is illustrated. In more detail, figure 5 shows the received microwave signals from three different measurements together with a criterion. Only the microwave signals completely confined by the upper and lower limits are determined to represent a measurement situation with good fitting of antennas, matching material and damping material and all cables and antennas are functioning properly. Microwave signals outside of the bounds in any part are used as detection criterion for a non-functioning system. The x-axis of figure 5 represents f/GHz and the y-axis represents S/dB. This figure 5 shows three different measurements when reflected signals, represented as S-parameters, have been collected, e.g. s1 1 , and the corresponding curves 505, 507 are shown. Two curves 507 are measured with good fitting of the antenna 105 to the body 103, i.e. there is no space 5 1 16 or a space 1 15 between the antenna 105 and the body 103, the size of the space 1 15 may be only a millimetre in length or smaller to be detected. Two curves 505 represent measurements with a bad fitting of the antenna 105 to the body 103, i.e. there is a space 1 15 between the antenna 105 and the body 103. Also, two lines are shown in figure 5 to exemplify an upper 501 and a lower 503 bound. These bounds may constitute a criterion0 within which a measured scattered/received microwave signal may be confined to be determined as good, with good fitting of antennas 105 to the body 103. The upper 501 and lower 503 bounds may be determined from measurements, simulations or calculations when the fit of the antennas 105 to the body 103 are known to be good. In the same way, one can confine within an upper 501 and lower 503 bound measurements also5 with good fitting of also the first dielectric material 1 1 1 and second dielectric material 1 13 known to be in place.

The criterion for an acceptable measurement, i.e. a god fit, may be the same for all antennas 105, they may be different for all antennas 105 or they may be the same for0 some of the antennas 105 and different for other antennas 105.

One or more of the microwave transmitting/receiving unit 13, the analyzer 14 and the display unit 15 illustrated in figure 1 may be incorporated into the system, e.g. one of the antennas 105 in the system. In another embodiment, all modules illustrated in figure 15 may be separate standalone modules. In a further embodiment, some of the modules illustrated in figure 1 may be co-located with each other, for example, the microwave transmitting/receiving unit 13, and the analyzer 14 may be co-located in one module and the microwave transmitting/receiving unit 13 and the system may be co-located in one module. The analyzer 14 may be for example a processor. In addition, the system may0 comprise at least one memory (not shown in figure 1 ) which may be adapted to store the received/scattered microwave signals.

Some embodiments described herein may be summarised in the following manner: A method for determining antenna fit of at least one antenna 105 positioned outside a body 103. The body 103 is surrounded by a medium 107. At least the body 103 and the medium 107 have different dielectric properties. The method comprising:

• Transmitting one or multiple microwave signal(s) from the at least one antenna 105 towards the body 103. A first part of the microwave signal leaves the antenna and is first reflected and/or scattered from the surface of the body 103 and a second other part is entering the body 103.

• Receiving the one or multiple reflected and/or scattered microwave signal(s) at another antenna 105 or at the transmitting antenna 105 whereby it is operated as a receiver after it has transmitted or operated as a receiver at the same time as it is transmitting.

• Comparing the received microwave signal(s) with at least one other microwave signal or a criterion determined from measurements of the received microwave signals when the at least one antenna 105 is known to be fit to the body 103, · Based on the comparing, determining if the at least one antenna 105 is fit to the body 103 or not.

The method may be performed by a system. The microwave signal(s) received by the at least one antenna 105 may be used to detect an internal object 105 in the body 103.

The at least one antenna 105 may be determined to have a good fit when all received microwave signals fulfils the criterion, wherein the criterion is associated with the received microwave signal(s).

The at least one antenna 105 may be determined to not fit when any of the received microwave signal does not fulfil the criterion. The criterion may be associated with the received microwave signal(s).

The criterion may be that all received microwave signals are between an upper boundary 501 and a lower boundary 503, or the criterion may be that all received microwave signals should be on or above the upper boundary 501 , or the criterion may be that all received microwave signals should be on or below the lower boundary 503. The at least one antenna 105 may be determined to fit when the received microwave signals representing contact between the body 103 and the antenna 105 is substantially confined within thane upper boundary 501 and a lower boundary 503 in at least one frequency.

The criterion may be associated with an S-, z-, y-, h-, t- parameter or ABCDE-parameters, reflection coefficients, insertion loss, a percentage parameter, a magnitude parameter, a phase parameter, a time-domain pulse or any other representation of the received microwave signals.

The method may further comprise:

• Determining that transmitting and/or receiving microwave signals for detection of the internal object 100 can start when the at least one antenna 105 is determined to fit to the body 103; and

· Determining, when the at least one antenna 105 is determined to not fit to the body 103, that the at least one antenna's fit to the body 103 should be adjusted before starting transmitting and/or receiving microwave signals for detection of the internal object 100. The method may further comprise:

• Based on the comparing, identifying at least one of: a faulty antenna and/or a

broken cable when the received microwave signal is not confined within an upper boundary 501 and a lower boundary 503, even when the at least one antenna 105 is determined to have a good fit on the body 103.

A first dielectric material 1 1 1 may be adapted to be located between the antennas 105 and the body 103.

A first dielectric material 1 1 1 may be adapted to be located between the at least one antenna 105 and the body 103 and may be determined to fit when the received microwave signals representing contact between the body 103, the first dielectric material 1 1 1 and the at least one antenna 105 is substantially confined within an upper boundary 501 and a lower boundary 503. A first dielectric material 1 1 1 may be adapted to be located between the at least one antenna 105 and the body 103 and may be determined to not fit when any of the received microwave signal does not fulfil the criterion. A second dielectric material 1 1 1 may be located between two antennas 105, and/or next to a single antenna 105.

At least two antennas 105 may be positioned outside a body 103. A second dielectric material 1 1 1 may be adapted to be located between the antennas 105 and may be determined to fit when the received microwave signals representing contact between the second dielectric material 1 1 1 and the antennas 105 is confined within the upper boundary 501 and the lower boundary 503.

At least two antennas 105 may be positioned outside a body 103. A second dielectric material 1 1 1 may be adapted to be located between the antennas 105 and may be determined to not fit when any of the received microwave signal does not fulfil a criterion.

The method may further comprise:

detecting movement of at least one of: the antenna 105 and/or the body 103, and/or the first dielectric material 1 1 1 and/or the second dielectric material 1 1 1 .

The method may further comprise:

• detecting movement of at least one of: the antenna 105 and/or the body 103 and/or the first dielectric material 1 1 1 and/or the second dielectric material 1 1 1 by comparing the received microwave signals to the criterion.

An ongoing detection of the internal object 100 may aborted when the movement is detected. Microwave signals received during the detected movement may be discarded or marked as corrupt after completion of the transmission and receipting of microwave signals.

The method may further comprise:

• providing information indicating a result of the determining to an operator. The method may further comprise:

• obtaining a representation of the received microwave signal.

The representation of the received microwave signal may be used when comparing the received microwave signals.

The representation of the received microwave signal at a receiver antenna 105 may be normalized with a common normalization factor before comparing the received microwave signals. The representation of the received microwave signal may be in the form of pairs of a S-, Z-, y-, h-, t- parameter or ABCDE-parameters, reflection coefficients, insertion loss, a percentage parameter, a magnitude parameter, a phase parameter, a time-domain pulse or any other representation of the received microwave signals. The transmitted microwave signals may be in the frequency range of 100MHz-10GHz.

The body 103 may be a human body part, an animal body part, it may be made of biological tissue, wood, plastic or any other non-organic or organic material. The internal object 100 may be solid, semisolid, liquid or gas. The internal object 100 may represents a bleeding, a clot, an ongoing bleeding, a reoccurring bleeding, a tumour, a malignant lesion, a haemothorax, a pneumothorax, a defect in wood, a knot, a nail, a tree rot, an impurity or any internal object with different dielectric properties than the body (03.

The method may further comprise:

• determining to stop transmitting microwave signals or to disregard the received reflected and/or scattered microwave signal(s) when the at least one antenna 105 is determined to not fit the body 103.

A system for determining antenna fit of at least one antenna 105 positioned outside a body 103. The body 103 is surrounded by a medium 107. At least the body 103 and the medium 107 have different dielectric properties. The system is adapted to:

• Transmit one or multiple microwave signal(s) from the at least one antenna 105 towards the body 103. A first part of the microwave signal leaves the antenna and is first reflected and/or scattered from the surface of the body 103 and a second other part is entering the body 103. • Receive the one or multiple reflected and/or scattered microwave signal(s) at another antenna 105 or at the transmitting antenna 105 whereby it is operated as a receiver after it has transmitted or operated as a receiver at the same time as it is transmitting.

· Compare the received microwave signal(s) with at least one other microwave signal or a criterion determined from measurements of the received microwave signals when the at least one antenna 105 is known to be fit to the body 103.

• Based on the comparing, determine if the at least one antenna 105 is fit to the body

103 or not.

The microwave signal(s) received by the at least one antenna 105 may be used to detect an internal object 105 in the body 103.

The at least one antenna 105 may be determined to have a good fit when all received microwave signals fulfils the criterion. The criterion may be associated with the received microwave signal(s).

The criterion may be that all received microwave signals are between an upper boundary 501 and a lower boundary 503, or the criterion may be that all received microwave signals should be on or above the upper boundary 501 , or the criterion may be that all received microwave signals should be on or below the lower boundary 503.

The at least one antenna 105 may be determined to fit when the received microwave signals representing contact between the body 103 and the antenna 105 is substantially confined within thane upper boundary 501 and a lower boundary 503 in at least one frequency.

The criterion may be associated with an S-, z-, y-, h-, t- parameter or ABCDE-parameters, reflection coefficients, insertion loss, a percentage parameter, a magnitude parameter, a phase parameter, a time-domain pulse or any other representation of the received microwave signals. The system may be further adapted to:

• Determine that transmitting and/or receiving microwave signals for detection of the internal object 100 can start when the at least one antenna 105 is determined to fit to the body 103.

• Determine, when the at least one antenna 105 is determined to not fit to the body

103, that the at least one antenna's fit to the body 103 should be adjusted before starting transmitting and/or receiving microwave signals for detection of the internal object 100.

The system may be further adapted to:

• Based on the comparing, identify at least one of: a faulty antenna and/or a broken cable when the received microwave signal is not confined within an upper boundary 501 and a lower boundary 503, even when the at least one antenna 105 is determined to have a good fit on the body 103.

A first dielectric material 1 1 1 may be adapted to be located between the antennas 105 and the body 103. A first dielectric material 1 1 1 may be adapted to be located between the at least one antenna 105 and the body 103 and may be determined to fit when the received microwave signals representing contact between the body 103, the first dielectric material 1 1 1 and the at least one antenna 105 is substantially confined within an upper boundary 501 and a lower boundary 503.

A first dielectric material 1 1 1 may be adapted to be located between the at least one antenna 105 and the body 103 and may be determined to not fit when any of the received microwave signal does not fulfil the criterion. A second dielectric material 1 1 1 may be located between two antennas 105, and/or next to a single antenna (105).

At least two antennas 105 may be positioned outside a body 103, i.e. two or more antennas 105 may be positioned outside the body 103. A second dielectric material 1 1 1 may be adapted to be located between the antennas 105 and may be determined to fit when the received microwave signals representing contact between the second dielectric material 1 1 1 and the antennas 105 is confined within the upper boundary 501 and the lower boundary 503. At least two antennas 105 may be positioned outside a body 103, and a second dielectric material 1 1 1 may be adapted to be located between the antennas 105 and may be determined to not fit when any of the received microwave signal does not fulfil a criterion.

The system may be further adapted to:

· Detect movement of at least one of: the antenna 105 and/or the body 103, and/or the first dielectric material 1 1 1 and/or the second dielectric material 1 1 1 .

The system may be further adapted to:

• Detect movement of at least one of: the antenna 105) and/or the body 103 and/or the first dielectric material 1 1 1 and/or the second dielectric material 1 1 1 by comparing the received microwave signals to the criterion.

An ongoing detection of the internal object 100 may be aborted when the movement is detected.

Microwave signals received during the detected movement may be discarded or marked as corrupt after completion of the transmission and receipting of microwave signals.

The system may be further adapted to:

· Provide information indicating a result of the determining to an operator of the system.

The system may be further adapted to:

• Obtain a representation of the received microwave signal.

The representation of the received microwave signal at a receiver antenna 105 may be normalized with a common normalization factor before comparing the received microwave signals. The representation of the received microwave signal may be in the form of pairs of a S-, Z-, y-, h-, t- parameter or ABCDE-parameters, reflection coefficients, insertion loss, a percentage parameter, a magnitude parameter, a phase parameter, a time-domain pulse or any other representation of the received microwave signals.

The transmitted microwave signals may be in the frequency range of 100MHz-10GHz.

The body 103 may be a human body part, an animal body part, it may be made of biological tissue, wood, plastic or any other non-organic or organic material. The internal object 100 may be solid, semisolid, liquid or gas. The internal object 100 may represent a bleeding, a clot, an ongoing bleeding, a reoccurring bleeding, a tumour, a malignant lesion, a haemothorax, a pneumothorax, a defect in wood, a knot, a nail, a tree rot, an impurity or any internal object with different dielectric properties than the body 103.

The system may be further adapted to:

• Determine to stop transmitting microwave signals or to disregard the received reflected and/or scattered microwave signal(s) when the at least one antenna 105 is determined to not fit the body (03.

A computer program may comprise instructions which, when executed on at least one processor, cause the at least one processor to carry out the method described above. A carrier may comprising the computer program. The carrier may be one of an electronic signal, optical signal, radio signal or computer readable storage medium.

The embodiments herein are directed towards applications where the purpose is to detect an internal condition in an enclosed volume. The internal condition is represented by the internal object 100 and the enclosed volume is represented by the body 103. A few example applications have been presented above, such as medical diagnosis for obtaining information about internal objects 100 of human or animal body 103. However, one of skill in the art would appreciate that the example embodiments discussed may be used in any type of application utilizing scattered signals for the purpose of monitoring, detection, and/or diagnosis. For example, the embodiments presented herein may be utilized for various bodies 103 such as trees, buildings, etc. Various different types of internal objects 100 may be monitored, for example, the presence of a particular liquid 100 in the enclosed volume 103. The body 103 may be a patient and the internal object 100 may represent a medical condition, which manifests itself as a dielectric contrast with respect to the healthy tissue comprised in the body 103. The body 103 may also be a tree and the internal object 100 may represent tree health, which manifests itself as a dielectric contrast with respect to the healthy wood. In principle, all internal conditions of a body 103 which can be expressed as a dielectric contrast, where the dielectric property of the internal condition is different from the healthy or normal background tissue.

One area of application for the embodiments herein is in microwave applications intended for diagnosing stroke patients by means of a system that can be used in an ambulance or a pre-hospital setting for assessments of patients with suspected stroke. The system could also be used at the hospital for assessment of patients with suspected stroke. The embodiment herein are used for detecting if antennas 105 have a good fit to the body 103 as well to ensure that matching medium 1 1 1 and damping material 1 13 are correctly fitted and functioning. Also broken antennas 105 and associated cables can be detected. Thus the embodiments presented herein help secure high quality in measured signals and thus helps to make a correct diagnosis of the stroke.

The embodiments presented herein could for example be used in microwave based methods intended for various monitoring applications. It could be monitoring of patients with an increased risk of getting a stroke. Monitoring could be made during sleep or while the patient lies down in bed, or with compact wearable systems during daytime. In patients that have had a bleeding it could be used to detect if the bleeding starts over. There exist also a number of other monitoring situations where it is of interest to monitor the occurrence, presence, or changes in a present bleeding, or other types of liquids, e.g. edemas, in the skull where a wearable version of the system could give a detection and a diagnosis. Applications, such as bedside intracranial monitoring will be possible where the pressure is coupled to the amount of liquid inside the skull. The embodiments herein could also be used in microwave based applications for other conditions, such as pre-hospital diagnostics of traumatic brain injury patients or monitoring of various conditions in the head at the neuro intensive care, or in other similar

applications. It would also be possible to apply the embodiments herein to diagnostics of other parts of the human body, e.g. the abdomen in case of suspected internal bleeding or the thorax for detection of pneumothorax or hemothorax. In that case, the system has to be suitably designed but the analysis could be done with the same equipment as for the brain applications.

The various embodiments described herein is described in the general context of method steps or processes, which may be implemented in one embodiment by a computer program product, embodied in a computer-readable medium, including computer- executable instructions, such as program code, executed by computers in networked environments. A computer-readable medium may include removable and non-removable storage devices including, but not limited to, Read Only Memory (ROM), Random Access Memory (RAM), compact discs (CDs), digital versatile discs (DVD), USB, Flash, HD, Blu- Ray, etc. Generally, program modules may include routines, programs, objects, components, data structures, etc. that performs particular tasks or implement particular abstract data types. Computer-executable instructions, associated data structures, and program modules represent examples of program code for executing steps of the methods disclosed herein. The particular sequence of such executable instructions or associated data structures represents examples of corresponding acts for implementing the functions described in such steps or processes.

The embodiments herein relate to a device, method, and system for assessing instrument status, system status, and determining if the antennas are in contact with the body and matching material and damping material before measurements are made to determine properties of the internal part of a body using an electromagnetic transceiver operating in the microwave regime; a processing unit compares measured signals with prescribed limits within which the measurements need to fall in order for the measurement setup to be properly made. Signals falling outside the limits may be an indication that the system must be adjusted or even repaired before measurements can be made. The solution may be arranged to continuously monitor the internal part of the body and the system may be arranged to as to be wearable or portable. Application areas

The embodiments herein deals with improvements in the measurement data quality in a system for detection of one or more dielectric target, with certain properties, such as size, shape, position, dielectric parameters, etc. that is immersed inside another dielectric medium. One area of application may be in diagnosing stroke patients by means of a sensor system that can be used in an ambulance or a pre-hospital setting for assessments of patients with suspected stroke. The same system could also be used at the hospital for assessment of patients with suspected stroke. This may help to reduce the time from the occurrence of the stroke till the time of making a correct diagnosis of the stroke. Delays in the diagnosis is today a major problem as many patients don't get a diagnosis in time, and therefore treatment are often significantly delayed with dramatic consequences for the patients. Delays in the treatment increases the risk of severe injuries, handicaps, and even death.

Internationally, ambulance service paramedics have been trained to use a stroke recognition tool to speed up transfer and assessment of patients with suspected stroke. This facilitates the time critical intervention of thrombolysis which has been shown to improve the outcome from ischemic stroke if given in time. Even with the best efforts today, many patients still don't get the treatment in time. Additional information may be provided at an earlier time than today in the chain of care, and makes it possible to distinguish between healthy people and stroke patients, and further to diagnose between ischemic and hemorrhagic stroke. Deployed for example in ambulances, or in any prehospital setting, or at the arrival point of ambulances at hospitals, earlier diagnosis may be facilitated and thus enables earlier treatment.

Other examples of applications are for various monitoring applications. It could be monitoring of patients with an increased risk of getting a stroke. Monitoring could be made during sleep or while the patient lies down in bed. Or with compact wearable systems during daytime. If the system detects an occurrence of a stroke it will immediately trigger an alarm to alert that a stroke has occurred, and also immediately give a diagnosis whether it was a bleeding or a clot. It could also be used for monitoring of patients that undergo thrombolytic treatment. In this case, it is of interest to monitor if the treatment is effective, the clot resolved and the circulation restored. In patients with a bleeding stroke the system could be used for monitoring if the bleeding is ongoing or if it has stopped. In patients that have had a bleeding it could be used to detect if the bleeding starts over. There exist also a number of other monitoring situations where it is of interest to monitor the occurrence, presence, or changes in a present bleeding, or other types of liquids, e.g. edemas, in the skull where a wearable version of the antennas could give a detection and a diagnosis. Applications, such as bedside intracranial monitoring will be possible where the pressure is coupled to the amount of liquid inside the skull.

The methods described here could also be used in other conditions, such as pre-hospital diagnostics of traumatic brain injury patients or monitoring of various conditions in the head at the neuro intensive care, or in other similar applications. It would also be possible to extend the method to include diagnostics of other parts of the body, e.g. the abdomen in case of suspected internal bleeding or the thorax for detection of pneumothorax or hemothorax. In that case the antenna system has to be suitably designed but the analysis could be done with the same equipment as for the brain applications.

In principle, all conditions inside a body where there is a dielectric contrast and/or where the level of dielectric contrast changes over time could be detected. The body could be humans, animals, or any other form of biological tissue. In general, it could be any solid, semisolid, liquid or gas. The interior of a larger object/body can be interrogated and detect the presence, occurrence of variations in the properties of one or more immersed objects with different dielectric property than that of the larger object.

This embodiments herein deal with the sensing of internal objects inside a larger object. It is accomplished by illuminating the larger object with electromagnetic radiation that is propagating through and scattered from the different immersed objects. The scattered radiation is carrying the information utilized an analyzed for the purpose of detecting and analyzing possible objects, e.g. abnormalities inside. The large object could be a skull, a torso, a leg or some other body part. But the objects could also be non-living tissue, and of non-biological origin, such as but not limited to wood, plastics etc.

A system may comprise signal generator, an applicator, i.e. an antenna system, a signal receiver, a converter, an analyzer and a screen or a different device for presenting the result, se Figure 1 . The transmitter/receivers transmit and receive electromagnetic signals. The measured data is collected for instance from continuous wave data measured at single or multiple discrete frequencies, or from pulsed or p-n sequence data. The signals are spanning a given and pre-defined frequency range. The frequency range may be for example but not limited to 100 MHz to 5 GHz or more. The frequency interval can be narrower but also wider. Based on the measured data, transmission and/or reflection data, for example but not limited to S-parameter data are calculated in the converter module. S-parameter data, or other representations of the measured data, are calculated from the transmitted and/or received signals and then fed to the analyzer. The result from the analyzer is presented on a screen or some other relevant device. The antenna system, constitutes the interface between the microwave system and the body under investigation, and it consists of at least one transmitter of electromagnetic waves, e.g. an antenna, that is placed outside the object under investigation and arranged to send electromagnetic signals into the body. The antennas transmitting and receiving the microwaves are connected to a signal generator and a receiving unit respectively. One or more receivers outside the object under investigation are detecting the scattered radiation which is later processed by an algorithm for data analysis and diagnosis.

Antennas can be monopoles, patches, horns, etc. or any type of antenna. Other types of emitters and or receivers can be used. The system may consists of a configuration of at least one antenna acting both as transmitter and receiver. In another embodiment, it may consist of at least one separate transmitter and at least one separate receiver positioned around the object under investigation. In yet another embodiment it may consist of at least two antennas acting both as transmitters and receivers. A possible operation is that all antennas in turn, are used as transmitters while the rest of the antennas are receiving. A measurement when all combinations of antennas are used as transmitter-receiver pairs are denoted a "full measurement set" in the following text. To obtain time resolution data, several "full measurement sets" after each other are collected during a period of time. Or alternatively, several partial measurement sets are measured, meaning that only a subset of all antennas are used as transmitters and/or receivers.

In one embodiment, the system may be setup to generate microwave signals and take measurements that are used to calculate, for example but not limited, to S-parameter data in the desired frequency range between the transmit-receive antenna combinations. S- parameters are only an example. Other examples of common representations of measurement data that could work equally well are z, y or h-parameters, reflection coefficients, insertion loss, etc. Data can be collected at one or more frequencies in the range. Data collected in time-domain or in frequency domain are both related by the Fourier Transformation. From a point of data analysis, the two different sets of data are of equal value. The measurement electronics for frequency domain measurements, or pulsed measurements differ.

The measured data, represented for example as the calculated S-parameter data, is transferred to an analyzer. The analyzer extracts the necessary information from the measured data and processes the data with an algorithm in order to perform the detection. The detections are based on a dielectric contrast between the immersed object/objects that are being detected and the larger object immersing them. The object that are detected could be a gas, liquid, a solid or a semisolid substance that is immersed inside another dielectric object. They should have different dielectric properties to create a detectable contrast.

Basic use of the system

One possible use of a system according to the description above is detection and monitoring of dielectric objects by microwave tomography utilizing the dielectric contrasts between the different parts of objects and the effects that has on the measured data.

One possible use of a system according to the description above is detection and monitoring of dielectric objects by classification utilizing the differences in the dielectric contrasts between the different classes of objects and their effects on the measured data. It could be the classifier described in the patent "Classification of microwave scattering data" with application number US 13/386,521 , or it could be any other classification algorithm. One possible use of a system according to the description above, and the basic use of the system above is detection and monitoring of dielectric objects that are for example but not limited to expanding, decreasing its size, changing its shape, or changing its properties or moving while the measurements are ongoing. The object may be manifested in the measurements in terms of the transmission and reflection data, for example but not limited to, the S-parameters, the received pulsed data, or the received p-n sequence data.

During a measurement using the system there is at least one antenna transmitting and at least one antenna receiving part of the transmitted signal. The measurements can be made once, or multiple times either with a pause between the measurements, or continuously.

Success of the detection and monitoring of dielectric objects using microwave tomography or classification algorithms is based on a dielectric contrast between the object that is being detected and the background. However, the background is not necessary homogeneous.

Assuming that the object, to be detected or monitored, is a liquid, a solid, a gas or a semisolid substance, immersed inside another dielectric object, with different dielectric properties. This may be denoted "the object under test" (OUT) and the immersed object to be detected is denoted "the immersed object" (10) . This object under test may be surrounded by a third dielectric material that could for example be air, and denoted background medium (BGM). See figures 2a-d. The dielectric properties of these three different materials are different. At least the OUT have different properties than the 10. The dielectric properties of the OUT and the BGM could be the same.

In performing the measurement with the system, the system is fitted to the object under test (OUT), where the immersed object (10) to be detected or monitored is immersed inside.

Part of the energy transmitted from the transmitting antenna is entering the object under test. The portion of this energy that is scattered off the 10 and leaving the OUT and received by the antennas is useful for detection purposes. The part of the energy that is not entering the OUT, is reflected or transmitted outside or on the boundary of the object under test. This energy may not be so useful for detection purposes.

A system for detection of the quality of antenna fit against an object under test

The embodiments herein relate to a radio/microwave antenna system, for example according to the description above, where the antennas are pressed against a body, (i.e. an OUT). The embodiments herein describe a method to detect if the antenna(s) have a good fit to the body (OUT) or not. This information can for example be used to determine if conditions for starting to send and/or receive on the antenna(s) are good enough or not or if the antenna fit to the body should be adjusted first. The fact that the dielectric properties of the body (OUT) is different from the dielectric properties of the ambient , (or the background medium, BGM), e.g. air, is exploited. The differing dielectric properties will result in different antenna characteristics. The reflection characteristics, e.g. s-parameter s1 1 , of the antenna is measured and compared to the same antenna characteristics in the ambient and to a measurement with a good fit of the antenna to a body of the same (or similar) dielectric properties. If the reflection characteristics are sufficiently close to that of a body of the same (or similar) dielectric properties as the one to be used, then the fit is deemed to be good. If the reflection characteristics are shifted towards the characteristics of the antenna in the ambient, then the fit is deemed to be poor.

In Figure 5, three reflection characteristics curves are shown. Here a network analyzer may have been used to determine the reflection coefficients, s1 1 , over a frequency interval. One curve is a measurement done where the antenna is transmitting into air, (only BGM present, no OUT). Another curve is from a measurement where the antenna was properly pressed against a body (OUT) with a relative dielectric constant higher than air. Yet a further curve is a measurement done on an antenna which is poorly pressed against the same body. It is clear that the red curve is in-between two of the curves. Also in Figure 5, are two solid lines, representing an upper and a lower bound for an example criterion. This example criterion could be used to determine if a fit shall be deemed as good or as bad. The fit is determined to be good if the all data fall in between the two black lines and deemed poor if any data is located outside the area between the two curves at any frequency. As can be seen, both the blue (air) and the red (poor fit) fall outside the limits for a good fit. There are of course many other ways to define such criterion, e.g. by the location or the depth of the minimum in the reflection data. The measurement and criterion could be done over a larger or smaller frequency range of even for a single frequency point. Another possibility is that only one of the two criteria are specified, i.e. either a lower or an upper criterion.

In the example in Figure 5 the black lines represent an upper limit and a lower limit respectively for the measured S-parameter data. These limits can be deduced from measurements or modelling in situations relating to correct fit of the antennas or to improper fit of the antennas. A basic condition when determining the limits is that the measurements representing the good contact between the body and the antenna is in every frequency point confined within the upper and the lower criteria. The black lines can be arbitrarily chosen, and the closer the black lines are the measurement data of a good fit, the more restrictive the criterion. This could also be a method to identify faulty antennas, broken cables etc. A faulty antenna or a broken cable will manifest itself as a change in impedance and cause additional reflections and scattering of signals in the cable or antenna. This will result in a corresponding change in the measured data, for example the reflection coefficients. If measured data is represented as S-parameters. In many cases the S-parameters, at least at some frequency points, will fall outside the upper and lower limits in cases where such faults occur.

In a multi-antenna system, the reflection measurement test could be done for each antenna or a subset of antennas. The condition could be deemed good only if all antennas pass the given criterion or each antenna could be judged and

approved/disapproved individually. The criteria could be identical for all antennas or they could be individual for each antenna depending on the antenna and its environment.

Matching bags

During a measurement using the system, there may be an interest to optimize, for example maximize, the part of the energy transmitted from the transmitting antenna that enters into to OUT. This would in turn optimize, for example minimize, the energy that is reflected or transmitted outside or on the boundary of the OUT. Optimize is here taken to mean the energy levels that improves, for example, maximizes, the abilities of the system.

For this purpose, a dielectric material may be put between the antennas and the OUT." We call this material "matching bags".

The shape, including thickness, and the dielectric properties of this dielectric material are then to be determined in a way that improves, for example maximizes, the abilities of the system.

One possible way to achieve this is to perform computer simulations of the full system, including the dielectric material, and let the computer optimize the performance of the system by varying the shape, including the thickness, and the dielectric properties of the dielectric material.

One possible way to achieve this is to minimize the reflected power, for example by minimizing the reflected power as indicated by the measured, calculated or simulated reflection coefficients by varying the shape, including the thickness, and the dielectric properties of the dielectric material.

Blocking of signal paths outside the OUT

During a measurement using the system, there could be of interest to optimize, for example minimize, the part of the energy transmitted from the transmitting antenna that enters into to the, BGM. The BGM surrounds the OUT. Signals that propagate along a path that never enters the OUT, from transmitting antennas to the receiving antennas, are unwanted and could cause disturbance and inaccuracies to the detection ability. The disturbing signals could be surface waves along the surface of the OUT, or along cables and other structures of the system. IT could also be signals that propagate solely in the BGM.

For this purpose, a dielectric material may be put on the side of the antennas, between the antennas and the BGM. The BGM surrounds the OUT. The added dielectric material could dampen, i.e. absorb, the waves but could in principle also be reflective, and even metallic or magnetic.

The shape, including thickness, and the dielectric properties of this dielectric material are then determined such that it improves, for example maximizes, the abilities of the system.

One possible way to determine the shape, the thickness and dielectric properties is to perform computer simulations, measurements, or a combination thereof. These parameters are system specific and must be determined for every specific design of the system.

If using computer simulations, a numerical model of the antenna system is used and the dielectric material is inserted in the model, between the antennas, according to Figure 5. The simulations are set up to optimize the performance of the system, for example minimize signals that propagate on paths between the antennas without entering into the OUT. The shape, the thickness and the dielectric properties are varied in the computer simulations in order to find the configuration resulting in the best system performance.

If using measurements, a real antenna system is used, dielectric material is then introduced in the model. The shape, the thickness and the dielectric properties are varied in the experiment in order to find the configuration resulting in the best system

performance.

One possible way to optimize the shape and properties of the dampening material between the antennas in a specific system is to minimize the reflected power from transmitting antennas. This could be done by means of measured, calculated or simulated reflection coefficients by varying the shape, including the thickness, and the dielectric properties of the dielectric material such that the reflected power is minimized. A system for movement detection for improved measurement quality

A movement detection system may provide improved measurement accuracy.

To generate the best possible measurements the antenna systems and the object that is measured should be completely still. Movements of the object under test, OUT, the antenna system or both during measurements will give artefacts in the measurements and there is a significant risk of faulty detections and diagnostics. The system may track movements of the head, the antenna system or both simultaneously.

In one embodiment, only relative motion between the antenna system and the head may be tracked.

It may be possible when there is no movement, of either the head, the antennas or both, is detected. In another embodiment, an ongoing measurement may be aborted if a movement is detected. In yet another embodiment, a measurement is allowed if movement is detected, but the data is discarded or marked as corrupt after completion of the measurements.

The movement detection can, for example but not limited to, consist of a system of accelerators, magnetometers, or other movement sensors that are attached to the skull. And in addition, a set of accelerators, magnetometers, or other movement sensors are further built into the antenna system to detect movements of the antennas. Absolute movements of the head and the antenna system can thus be tracked individually.

Alternatively, relative movement can be detected. In another example the movement tracking can be made with cameras, lasers or other technical equipment. Movements can also be detected with time of flight measurements of reflected electromagnetic pulses. Movements will cause a change in the distance between the antenna and the OUT that will manifest itself as a change in time of flight. Combined use of criteria for antenna fit, matching bags, dielectric material to block surface waves, and motion detection

One possible use of the system may be that all the parts described above are used together, i.e. matching bags, and with the criteria to ensure good fit of the matching bags and the antennas against the body. At the same time, dielectric material is introduced between the antenna to block surface waves. Finally, the system for motion tracking is used in order to ensure the system or object under test is still during the measurements.

Any number and combinations of these techniques can be used simultaneously or separately.

The embodiments herein are not limited to the above described embodiments. Various alternatives, modifications and equivalents may be used. Therefore, the above

embodiments should not be taken as limiting the scope of the embodiments, which is defined by the appending claims. A feature from one embodiment may be combined with one or more features of any other embodiment.

It should be emphasized that the term "comprises/comprising" when used in this specification is taken to specify the presence of stated features, integers, steps or components, but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof. It should also be noted that the words "a" or "an" preceding an element do not exclude the presence of a plurality of such elements. The terms "consisting of" or "consisting essentially of" may be used instead of the term comprising. Several "means" or "units" may be represented by the same item of hardware. The term "configured to" used herein may also be referred to as "arranged to", "adapted to", "capable of or "operative to".

It should also be emphasised that the steps of the methods defined in the appended claims may, without departing from the embodiments herein, be performed in another order than the order in which they appear in the claims.

Claims

1. A method for determining antenna fit of at least one antenna (105) positioned outside a body (103), wherein the body (103) is surrounded by a medium (107), wherein at least the body (103) and the medium (107) have different dielectric properties, the method comprising:

transmitting one or multiple microwave signal(s) from the at least one antenna (105) towards the body (103), wherein a first part of the microwave signal leaves the antenna and is first reflected and/or scattered from the surface of the body (103) and a second other part is entering the body (103)

receiving the one or multiple reflected and/or scattered microwave signal(s) at another antenna (105) or at the transmitting antenna (105) whereby it is operated as a receiver after it has transmitted or operated as a receiver at the same time as it is transmitting;

comparing the received microwave signal(s) with at least one other microwave signal or a criterion determined from measurements of the received microwave signals when the at least one antenna (105) is known to be fit to the body (103); and

based on the comparing, determining if the at least one antenna (105) is fit to the body (103) or not.

2. The method according to any one of claims 1 , wherein the microwave signal(s) received by the at least one antenna (105) is used to detect an internal object (105) in the body (103). 3. The method according to any one of claims 1-2, wherein the at least one antenna ( 05) is determined to have a good fit when all received microwave signals fulfils the criterion, wherein the criterion is associated with the received microwave signal(s).

4. The method according to any one of claims 1-3, wherein the at least one antenna (105) is determined to not fit when any of the received microwave signal does not fulfil the criterion, wherein the criterion is associated with the received microwave signal(s).

5. The method according to any one of claims 1-4, wherein the criterion is that all received microwave signals are between an upper boundary (501 ) and a lower boundary (503), or wherein the criterion is that all received microwave signals should be on or above the upper boundary (501 ), or

wherein the criterion is that all received microwave signals should be on or below the lower boundary (503).

6. The method according to any one of claims 1-5, wherein the at least one antenna (105) is determined to fit when the received microwave signals representing contact between the body (103) and the antenna (105) is substantially confined within thane upper boundary (501 ) and a lower boundary (503) in at least one frequency.

7. The method according to any one of claims 1-6, wherein the criterion is associated with an S-, Z-, y-, h-, t- parameter or ABCDE-parameters, reflection coefficients, insertion loss, a percentage parameter, a magnitude parameter, a phase parameter, a time-domain pulse or any other representation of the received microwave signals.

8. The method according to any one of claims 1-7, further comprising:

determining that transmitting and/or receiving microwave signals for detection of the internal object (100) can start when the at least one antenna (105) is determined to fit to the body (103); and

determining, when the at least one antenna (105) is determined to not fit to the body (103), that the at least one antenna's fit to the body (103) should be adjusted before starting transmitting and/or receiving microwave signals for detection of the internal object (100). 9. The method according to any one of claims 1-8, further comprising:

based on the comparing, identifying at least one of: a faulty antenna and/or a broken cable when the received microwave signal is not confined within an upper boundary (501 ) and a lower boundary (503), even when the at least one antenna (105) is determined to have a good fit on the body (103).

10. The method according to any one of claims 1-9, wherein a first dielectric material (1 11 ) is adapted to be located between the antennas (105) and the body (103).

1 1. The method according to any one of claims 1-10, wherein a first dielectric material (1 11 ) is adapted to be located between the at least one antenna (105) and the body (103) and is determined to fit when the received microwave signals representing contact between the body (103), the first dielectric material (1 11 ) and the at least one antenna (105) is substantially confined within an upper boundary (501 ) and a lower boundary (503).

12. The method according to any one of claims 1-1 1 , wherein a first dielectric material

(1 1 1 ) is adapted to be located between the at least one antenna (105) and the body (103) and is determined to not fit when any of the received microwave signal does not fulfil the criterion.

13. The method according to any one of claims 1-12, wherein a second dielectric material (1 1 1 ) is located between two antennas (105), and/or next to a single antenna (105).

14. The method according to any one of claims 1-13, wherein at least two antennas (105) are positioned outside a body (103), and

wherein a second dielectric material (11 1 ) is adapted to be located between antennas (105) and is determined to fit when the received microwave signals representing contact between the second dielectric material (1 1 1 ) and the antennas (105) is confined within the upper boundary (501 ) and the lower boundary (503).

15. The method according to any one of claims 1-14, wherein at least two antennas (105) are positioned outside a body (103), and

wherein a second dielectric material (1 1 1 ) is adapted to be located between the antennas (105) and is determined to not fit when any of the received microwave signal does not fulfil a criterion. 6. The method according to any one of claims 1- 5, further comprising:

detecting movement of at least one of: the antenna (105) and/or the body (103), and/or the first dielectric material (11 1 ) and/or the second dielectric material (1 11 ).

17. The method according to any one of claims 1 -16, further comprising:

detecting movement of at least one of: the antenna (105) and/or the body (103) and/or the first dielectric material (1 11 ) and/or the second dielectric material (1 11 ) by comparing the received microwave signals to the criterion.

18. The method according to any one of claims 16-18, wherein an ongoing detection of the internal object (100) is aborted when the movement is detected. 9. The method according to any one of claims 6- 8, wherein microwave signals 5 received during the detected movement is discarded or marked as corrupt after

completion of the transmission and receipting of microwave signals.

20. The method according to any one of claims 1-19, further comprising:

providing information indicating a result of the determining to an operator.

10

21. The method according to any one of claims 1-20, further comprising:

obtaining a representation of the received microwave signal, and

wherein the representation of the received microwave signal is used when comparing the received microwave signals.

15

22. The method according to claim 21 , wherein the representation of the received microwave signal at a receiver antenna (105) is normalized with a common normalization factor before comparing the received microwave signals.

20 23. The method according to any one of claims 21-22, wherein the representation of the received microwave signal is in the form of pairs of a S-, z-, y-, h-, t- parameter or ABCDE-parameters, reflection coefficients, insertion loss, a percentage parameter, a magnitude parameter, a phase parameter, a time-domain pulse or any other

representation of the received microwave signals.

25

24. The method according to any one of claims 1-23, wherein the transmitted microwave signals are in the frequency range of 100MHz-10GHz.

25. The method according to any one of claims 1-24, wherein the body (103) is a human 30 body part, an animal body part, it is made of biological tissue, wood, plastic or any other non-organic or organic material.

26. The method according to any one of claims 1-25, wherein the internal object (100) is solid, semisolid, liquid or gas.

35

27. The method according to any one of claims 1-26, wherein the internal object (100) represents a bleeding, a clot, an ongoing bleeding, a reoccurring bleeding, a tumour, a malignant lesion, a haemothorax, a pneumothorax, a defect in wood, a knot, a nail, a tree rot, an impurity or any internal object with different dielectric properties than the body (103).

28. The method according to any one of claims 1-27, further comprising:

determining to stop transmitting microwave signals or to disregard the received reflected and/or scattered microwave signal(s) when the at least one antenna (105) is determined to not fit the body (103).

29. A system for determining antenna fit of at least one antenna (105) positioned outside a body (103), wherein the body (103) is surrounded by a medium (107), wherein at least the body (103) and the medium (107) have different dielectric properties, the system being adapted to:

transmit one or multiple microwave signal(s) from the at least one antenna (105) towards the body (103), wherein a first part of the microwave signal leaves the antenna and is first reflected and/or scattered from the surface of the body (103) and a second other part is entering the body (103)

receive the one or multiple reflected and/or scattered microwave signal(s) at another antenna (105) or at the transmitting antenna (105) whereby it is operated as a receiver after it has transmitted or operated as a receiver at the same time as it is transmitting; compare the received microwave signal(s) with at least one other microwave signal or a criterion determined from measurements of the received microwave signals when the at least one antenna (105) is known to be fit to the body (103); and to

based on the comparing, determine if the at least one antenna (105) is fit to the body (103) or not.

30. The system according to any one of claims 29, wherein the microwave signal(s) received by the at least one antenna (105) is used to detect an internal object (105) in the body (103).

31 . The system according to any one of claims 29-30, wherein the at least one antenna (105) is determined to have a good fit when all received microwave signals fulfils the criterion, wherein the criterion is associated with the received microwave signal(s).

32. The system according to any one of claims 29-31 , wherein the at least one antenna (105) is determined to not fit when any of the received microwave signal does not fulfil the criterion, wherein the criterion is associated with the received microwave signal(s).

33. The system according to any one of claims 29-32, wherein the criterion is that all received microwave signals are between an upper boundary (501 ) and a lower boundary (503), or

wherein the criterion is that all received microwave signals should be on or above the upper boundary (501 ), or

34. The system according to any one of claims 29-33, wherein the at least one antenna (105) is determined to fit when the received microwave signals representing contact between the body (103) and the antenna (105) is substantially confined within thane upper boundary (501 ) and a lower boundary (503) in at least one frequency.

35. The system according to any one of claims 29-34, wherein the criterion is associated with an S-, z-, y-, h-, t- parameter or ABCDE-parameters, reflection coefficients, insertion loss, a percentage parameter, a magnitude parameter, a phase parameter, a time-domain pulse or any other representation of the received microwave signals.

36. The system according to any one of claims 29-35, being further adapted to:

determine that transmitting and/or receiving microwave signals for detection of the internal object (100) can start when the at least one antenna (105) is determined to fit to the body (103); and to

determine, when the at least one antenna (105) is determined to not fit to the body

(103), that the at least one antenna's fit to the body (103) should be adjusted before starting transmitting and/or receiving microwave signals for detection of the internal object

(100).

37. The system according to any one of claims 29-36, being further adapted to:

based on the comparing, identify at least one of: a faulty antenna and/or a broken cable when the received microwave signal is not confined within an upper boundary (501 ) and a lower boundary (503), even when the at least one antenna (105) is determined to have a good fit on the body (103).

38. The system according to any one of claims 29-37, wherein a first dielectric material 5 (1 1 1 ) is adapted to be located between the antennas (105) and the body (103).

39. The system according to any one of claims 29-38, wherein a first dielectric material

(1 11 ) is adapted to be located between the at least one antenna (105) and the body (103) and is determined to fit when the received microwave signals representing contact 10 between the body (103), the first dielectric material (1 1 1 ) and the at least one antenna (105) is substantially confined within an upper boundary (501 ) and a lower boundary (503).

40. The system according to any one of claims 29-39, wherein a first dielectric material 15 (1 11 ) is adapted to be located between the at least one antenna (105) and the body (103) and is determined to not fit when any of the received microwave signal does not fulfil the criterion.

41. The system according to any one of claims 29-40, wherein a second dielectric

20 material ( 11 ) is located between two antennas ( 05), and/or next to a single antenna (105).

42. The system according to any one of claims 29-41 , wherein at least two antennas (105) are positioned outside a body (103), and

25 wherein a second dielectric material (1 11 ) is adapted to be located between antennas (105) and is determined to fit when the received microwave signals representing contact between the second dielectric material (1 1 1 ) and the antennas (105) is confined within the upper boundary (501 ) and the lower boundary (503).

30 43. The system according to any one of claims 29-42, wherein at least two antennas (105) are positioned outside a body (103), and

wherein a second dielectric material (11 1 ) is adapted to be located between the antennas (105) and is determined to not fit when any of the received microwave signal does not fulfil a criterion.

35

44. The system according to any one of claims 29-43, being further adapted to:

detect movement of at least one of: the antenna (105) and/or the body (103), and/or the first dielectric material (11 1 ) and/or the second dielectric material (1 11 ).

5 45. The system according to any one of claims 29-44, being further adapted to:

detect movement of at least one of: the antenna (105) and/or the body (103) and/or the first dielectric material ( 11 ) and/or the second dielectric material (111 ) by comparing the received microwave signals to the criterion.

10 46. The system according to any one of claims 29-45, wherein an ongoing detection of the internal object (100) is aborted when the movement is detected.

47. The method according to any one of claims 29-46, wherein microwave signals received during the detected movement is discarded or marked as corrupt after

15 completion of the transmission and receipting of microwave signals.

48. The system according to any one of claims 29-47, being further adapted to:

provide information indicating a result of the determining to an operator of the system.

20

49. The system according to any one of claims 29-48, being further adapted to:

obtain a representation of the received microwave signal, and

25

50. The system according to claim 49, wherein the representation of the received microwave signal at a receiver antenna (105) is normalized with a common normalization factor before comparing the received microwave signals.

30 51. The system according to any one of claims 49-50, wherein the representation of the received microwave signal is in the form of pairs of a S-, z-, y-, h-, t- parameter or ABCDE-parameters, reflection coefficients, insertion loss, a percentage parameter, a magnitude parameter, a phase parameter, a time-domain pulse or any other

representation of the received microwave signals.

35

52. The system according to any one of claims 29-51 , wherein the transmitted microwave signals are in the frequency range of 100MHz-10GHz.

53. The system according to any one of claims 29-52, wherein the body (103) is a human body part, an animal body part, it is made of biological tissue, wood, plastic or any other non-organic or organic material.

54. The system according to any one of claims 29-53, wherein the internal object (100) is solid, semisolid, liquid or gas.

55. The system according to any one of claims 29-54, wherein the internal object (100) represents a bleeding, a clot, an ongoing bleeding, a reoccurring bleeding, a tumour, a malignant lesion, a haemothorax, a pneumothorax, a defect in wood, a knot, a nail, a tree rot, an impurity or any internal object with different dielectric properties than the body (103).

56. The system according to any one of claims 29-55, being further adapted to:

determine to stop transmitting microwave signals or to disregard the received reflected and/or scattered microwave signal(s) when the at least one antenna (105) is determined to not fit the body (103).

57. A computer program comprising instructions which, when executed on at least one processor, cause the at least one processor to carry out the method according to any one of claims 1 -28.

58. A carrier comprising the computer program of claim 57, wherein the carrier is one of an electronic signal, optical signal, radio signal or computer readable storage medium.